Liquid-liquid extraction process for the production of acrylic esters

Abstract

The invention relates to a liquid-liquid extraction process, comprising: the provision of a main input liquid stream, comprising at least one compound of interest and an excess compound; the provision of a liquid scrubbing stream; the extraction of the excess compound from the main input liquid stream by contact with the liquid scrubbing stream, making it possible to collect a main output liquid stream, depleted in excess compound with respect to the main input liquid stream; in which: the main input liquid stream and the liquid scrubbing stream exhibit a difference in density of less than or equal to 50 kg/m 3 and also an interfacial tension of less than or equal to 3 dyn/cm; and the extraction stage is carried out in a packed contactor with a ratio by weight as input liquid scrubbing stream/main liquid stream ranging from 0.3 to 0.5. The invention also relates to a process for the production of acrylic ester in which the production stream is treated by means of the above liquid-liquid extraction process.

The invention claimed is: 
     
       1. A liquid liquid extraction process, comprising the steps of:
 providing a main input liquid stream, comprising at least acrylic ester and an excess compound which is an alcohol; 
 providing a liquid scrubbing stream which is an aqueous stream; 
 extracting alcohol from the main input liquid stream by contact with the liquid scrubbing stream, thereby collecting a main output liquid stream, depleted in alcohol with respect to the main input liquid stream; 
 wherein: 
 the main input liquid stream and the liquid scrubbing stream exhibit a difference in density of less than or equal to 50 kg/m 3  and an interfacial tension of less than or equal to 3 dyn/cm; and 
 the extraction stage is carried out in a packed contactor having packing components with a specific surface greater than or equal to 200 m 2 /m 3  and with a ratio by weight as input liquid scrubbing stream/main liquid stream ranging from 0.3 to 0.5. 
 
     
     
       2. The process according to  claim 1 , in which:
 the excess compound is an alcohol selected from the group consisting of methanol ethanol, and mixtures thereof. 
 
     
     
       3. The process according to  claim 1 , in which the main input liquid stream comprises from 0.5% to 30% of excess compound, and/or in which the main output liquid stream comprises less than 2000 ppm of excess compound. 
     
     
       4. The process according to  claim 1 , in which the packed contactor comprises packing components exhibiting a diameter of greater than or equal to the critical diameter, expressed in m, resulting from the relationship d c =2.42×(S*gc/Δρ*g) 0.5 , S representing the interfacial tension between the main input liquid stream and the liquid scrubbing stream, expressed in N/m, Δρ representing the difference in density between the main input liquid stream and the liquid scrubbing stream, expressed in kg/m 3 , gc being the conversion factor for the gravitational constant (kg.m/N.s 2 ) and g being the gravitational constant (9.83 m/s 2 ). 
     
     
       5. A process for the production of acrylic ester comprising the steps of:
 feeding a reactor with acrylic acid, catalyst and alcohol; 
 withdrawing an acrylic ester stream at an outlet of the reactor; 
 liquid-liquid extraction of the acrylic ester stream by an aqueous stream, thereby collecting a purified acrylic ester stream, the liquid-liquid extraction being carried out according to the process of  claim 1 , wherein the main input liquid stream is the acrylic ester stream, the liquid scrubbing stream is the aqueous stream, the main output liquid stream is the purified acrylic ester stream, the compound of interest is the acrylic ester and the excess compound is the alcohol. 
 
     
     
       6. The process according to  claim 5 , in which the purified acrylic ester stream is additionally subjected to one or more distillation stages in order to remove additional organic compounds. 
     
     
       7. The process according to  claim 5  wherein the outlet of the reactor comprises a settling stage to collect an aqueous phase in addition to the acrylic ester stream, the aqueous phase being distilled to recover, on the one hand, a fraction rich in alcohol which is recycled to the reactor and, on the other hand, a fraction rich in water which is used as liquid scrubbing stream in the liquid-liquid extraction stage. 
     
     
       8. The process according to  claim 7 , comprising the step of collecting an aqueous stream enriched in alcohol at the end of the liquid-liquid extraction stage and combining this with the aqueous phase resulting from the reactor.